Last month, the Cassini spacecraft snapped pictures as one of Saturn's moons, Rhea, slipped behind another moon named Dione. Rhea is much bigger than Dione (949 miles vs. 695 miles across), but in these snapshots, Dione is much closer (900,000 miles vs. 1.4 million miles). The result: The two shadowed disks look almost like twins passing in the night.

The 32-frame sequence was taken over a 17-minute period on Feb. 20, but were not highlighted until Thursday's image release — which led NASA Watch's Keith Cowing to wonder why the Jet Propulsion Laboratory took so long.

• March 4, 2005 | 7:50 p.m. ETBehind bars, in the stars: The last time I heard from Walt Anderson, the multimillionaire entrepreneur who is now being jailed on
tax-evasion charges
, it was via voicemail. I was trying to get some details about a Swedish zero-gravity venture — and although Anderson acknowledged he was working on the project, he was only too happy to refer me to someone else. "I've already had my 15 minutes of fame," he said.

Among space buffs, Anderson is better-known for how he spent his money rather than how he made and managed it. He was the major investor in the unsuccessful Rotary Rocket venture, and he made international news for his efforts to extend Mir's life back in 2000, through a U.S.-Dutch-Russian venture called MirCorp. Even after
Mir was scuttled
in 2001, he had hopes of working with the Russians to launch a free-flying "Mini-Station" into space.

He soon soured on the Mini-Station idea, saying that he was "done being an angel investor for crackpot space enthusiasts." But he saw last year's success of SpaceShipOne as something of a
vindication
for private-sector space enterprises, and in his interview with the Post this week, he sounded as if he hadn't given up on the long-term vision: "I want to build my own space station since we lost the Mir," he said. "I want to have a moon base."

In 2002, he started up a somewhat less ambitious venture, aimed at using "space tugs" to extend the operating life of aging telecommunications satellites. The London-based, privately held venture is now known as Orbital Recovery Ltd., and although Anderson himself is out of circulation, Orbital Recovery is just getting revved up.

The first space tug, known as the CX-OLEV, is about to go into production, with the first commercial launch scheduled 36 months later, said spokesman Jeff Lenorovitz.

"Walt Anderson contributed to the early stages of the structure of Orbital Recovery. He has not been involved in the operations of the company for some time," Lenorovitz told me. "The recent events are a personal matter for Mr. Anderson and have no relevance to the company."

As for the Swedish zero-gravity venture that captured Anderson's interest: At last report, Xero was gearing up for operations in association with the Icehotel in Kiruna and other tourism services.

The business plan called for providing zero-G rides in a rented Russian IL-76 jet, the kind used for cosmonaut training. And that's where Anderson's connections came into play: MirCorp assisted in putting together the deal with the Russians. So even though Anderson is currently in deep trouble, some of the efforts he put in motion are still percolating along. You could even argue that the MirCorp model for private space investment served as a precedent for efforts such as Mojave Aerospace Ventures,
Virgin Galactic
and
Blue Origin
.

• March 3, 2005 | 8 p.m. ETA galaxy's last gasp: Cosmic destruction rarely looked so good. A snapshot captured by the Hubble Space Telescope shows a purple haze of hot young stars as the irregular galaxy NGC 1427A crashes into "a large gang of galaxies" called the Fornax cluster at 1.4 million mph. The rough arrowhead shape points in the direction of the galaxy's motion.

NASA / ESA / STScI

The irregular galaxy NGC 1427A is a spectacular example of what happens when a galaxy falls in with the wrong crowd. Its collision with a galaxy cluster in the constellation Fornax is causing disruption and a burst of hot young stars. The yellowish spiral galaxy seen in the background is much tamer, and much farther away.

The galaxy, 62 million light-years away in the constellation Fornax, is being scrunched in a collision with a reservoir of intergalactic gas. The resulting gravitational pressure is what's causing all the star formation. But in today's image release, Hubble Heritage scientists say the rush of starbirth is just a prelude to galaxy death.

"NGC 1427A will not survive long as an identifiable galaxy passing through the cluster," they report. "Within the next billion years, it will be completely disrupted, spilling its stars and remaining gas into intergalactic space within the Fornax cluster."

The yellowish spiral to the upper left of NGC 1427A is a background galaxy that's 25 times farther away. Its color tells scientists that the star-formation process is far less furious.

The picture was taken by Hubble's Advanced Camera for Surveys two years ago, and astronomers are studying it to verify predictions about the ages of the stars, based on their positions within the galaxy.

NGC 1427A's creative destruction also provides a window to processes more common in the early universe, the Hubble scientists say: "Such events are believed to have been very common during the early evolution of the universe, but the rate of galaxy destruction is tapering off at the present time."

Chris Parker, a longtime FOCL (Friend of Cosmic Log), pointed out the software on Aeroplane Heaven, and noted also that the software has required some tinkering. It sounds as if the first version of the model didn't include quite enough virtual jet fuel, based on this disclaimer on the download page:

"This is a revised aircraft config file which will correct the fuel loadout. ... Load her up and you'll have the correct fuel load for takeoff with 18,000 pounds of fuel aboard. Sorry for the inconvenience, and to anyone currently swimming about in the Pacific Ocean."

• March 3, 2005 | 8 p.m. ETMore sounds of science: It turns out that my list of downloadable (and streamable) science audio and video only scratches the surface. For another round of cosmic listening pleasure, check out Clark Lindsey's roundup of SpaceCasts.

• March 2, 2005 | 8:15 p.m. ETDownload the sound of science: The World Wide Web is serving as a laboratory for new strains of scientific experimentation ... in communication, that is.

For example, check out "Slacker Astronomy," a weekly series of podcast programs initiated last month by three astronomer/writers. Among the downloadable MP3 audio clips are discussions of dark matter ("the other white meat"), coronal mass ejections (which aren't as risque as they sound) and gamma-ray bursts.

It's fascinating to hear how the podcasts become slicker and hipper in a matter of mere weeks. By Week 3, co-host Pamela Gay is noting how one huge gamma-ray burst originated from a source 50,000 light-years away. "This means it happened about 50,000 years ago," she observed, "about the time the first humans entered Europe and North America, and when Dick Clark was born."

Aaron Price, who teams up with Gay and Travis Searle to put together the roughly five-minute podcasts, says in an e-mail that they're trying to take "the latest in astronomical news and make it bright and interesting."

"Right now we have about 1,000 subscribers and another 700 who listen via the Web site," he said. Not bad for the first month of programming.

"Slacker Astronomy" has plenty of precedents, including two long-running audio shows that trace their roots to radio:

The Space Show, hosted by David Livingston, is heard in the Seattle area over KKNW-AM, but you can also use the Web to listen to the real-time show or graze through downloadable archived shows going back to 2001. Livingston covers the whole cosmos, focusing particularly on space commercialization and tourism.

Earth & Sky covers a wide range of scientific subjects, from astronomy to zoology, in daily programs that are broadcast over commercial and public radio stations as well as satellite networks. You can also download five years' worth of archived shows.

Science @ NASA also makes its Web features available as downloadable MP3 files. The StarDate astronomy program archives its audio segments as RealAudio files, and "Star Gazer," the weekly sky guide hosted by the ever-ebullient Jack Horkheimer, offers scripts as well as the archived five-minute RealVideo segments.

Do you have your own sources for downloadable sight-and-sound science? Let me know and I'll pass along the appropriate links.

• March 2, 2005 | 8:15 p.m. ETThe last word? Why do performers who go last have a better chance of getting a high score in the judging? That may not turn out to be the case for this week's
"American Idol"
sing-off, but researcher Wändi Bruine de Bruin found that the rule generally held true over the long term in professionally judged competitions.

In response to Tuesday's item about the "serial position effect," a few Cosmic Log readers proposed explanations for the phenomenon. Here's a sampling of the feedback:

Lois Smith: "Having been on the judging end of several (local and regional) talent-oriented competitions, I’d like to comment on the 'last shall be first' phenomenon from a different viewpoint. Your commentary does not address this judging factor at all: When a judge views or hears the first competitor, he/she has nothing to compare their performance to. If scoring is done immediately, the tendency is to score 'harder' — or lower — for the first few contestants until a median is found. The concept is to allow room for a later, better performance score than the first competitor might deliver: 'If I give this performer a perfect score in this category, how do I score another performer who might do better?' The answer is to score the first performers — relatively — in the middle ranges, in anticipation of better performances yet to come. Thus, the later performances have the benefit of being compared against an established norm — and good performances that happen later in the competition are rated higher."

Gavin: "While the effect is evident, I question whether or not simple order has everything to do with judging results. The reason I usually want to be last is not out of any statistical anomaly of psychology, but because I perform better. When you have to beat an A, it's a lot easier to muster the performance to achieve A+. I believe this is also evident in many competitions, whether it be the American hockey Olympic victory or a timed race. Much of this statistical effect could be removed if you compared empirical contests such as racing, in which racers raced individually in a distinct order, with judged contests. The first racer has no bar against which to compare himself. The last racer is able to know that if he is just a quarter-second faster than he ran last time, the gold is his."

Jeff Cox: "I think it can also be said that a judge will more favorably treat someone or something if they identify with it. Examples: I was inclined to vote on "Idol" for a girl from Oklahoma because I'm from Oklahoma. In judging cars at a car show, most owners of Chevys who judge all cars will find their favorite to be a Chevy; the most owners of Mustangs who judge all cars will find their favorite to be a Mustang. Serial position may have an impact, but only if the bias factors are nil."

• March 1, 2005 | 8:30 p.m. ETThe last shall be first: Statistics from four decades' worth of contests confirm what talent-show competitors like the singers on
"American Idol"
have probably known for at least that long: It's good to go last.

The fact that judges tend to favor the latter performers in a contest, a phenomenon known as the serial position effect, is documented in a study published in the March issue of the journal Acta Psychologica. Carnegie Mellon University's Wändi Bruine de Bruin analyzed the results of Eurovision song contests conducted between 1957 and 1997, as well as world and European figure-skating competitions.

What she found could have implications not only for singers and skaters, but for test-takers and job applicants as well.

"A friend of mine asked to go last in a series of job interviews, after hearing about my research," Bruine de Bruin said in a news release. "She got the job. I like to think that she got the job because she has great skills, but order effects may have tipped the balance for her."

In the Eurovision contests — a conceptual grandparent to "American Idol" — the performance order was determined by random lottery, and the judges picked the winner after everyone sang. Statistics showed that the first performer won 6 percent of the time, while the last performer won 13 percent of the time.

That tendency to favor the performance that's fresher in your mind has been documented before, in competitions ranging from classical music festivals to synchronized swimming. Producers angling for an Academy Award take advantage of the serial position effect by scheduling the opening of potentially prizeworthy films toward the end of the year.

Bruine de Bruin's study goes further by looking at skating competitions, where the judges render their verdict after each performance rather than waiting until the end. You might think that's a fairer way to do it, but her analysis indicates that going with a step-by-step procedure has little effect. The first skater in the first round of competition won the top prize only 3 percent of the time, while the last skater in the first round won 8 percent of the time.

In fact, Bruine de Bruin thinks the procedure for a skating contest amplifies the unfairness, because the higher you score in the first round, the later you perform in the second and decisive round.

So what's the remedy? For multiple-round contests, Bruine de Bruin suggests shuffling the performance order so that the first go last — or at least conduct another lottery.

"The lottery doesn’t get rid of the effect," she told me today. "It just gives you a better chance of scoring better in the serial position."

Another, more radical remedy would be to weight the judging scores to favor earlier performers and cancel out the statistical serial position effect. "I would really strongly suggest that judges do not try to compensate for it themselves," Bruine de Bruin said. "If they try to correct for it, then people have a tendency to overcorrect."

Does the serial position effect rear its ugly head in the "American Idol" race? Bruine de Bruin doesn't know enough about the procedures for performance order and voting to handicap that competition. She stresses that her research focused on the behavior of professional judges rather than call-in voters. But she guesses that the dynamics are far more complex in a contest where millions of judges are encouraged to vote late and often.

"You can't control what they watch," Bruine de Bruin said, "so they may tune in later and then only vote for the people they have seen."

Are there twists in the "American Idol" procedures that tend to favor some singers over others? Let me know what you think, and I'll pass along a sampling of the feedback.

• March 1, 2005 | 8:30 p.m. ETMore greatest hits: Last week's list of top sources for cosmic imagery is missing at least one must-see astronomy Web site, as I was reminded by Georgia Sutton of Laramie, Wyo.: "I'm surprised that you did not mention the Astronomy Picture of the Day! Why not? It has a different image every day and an archive that goes back years!"

Please forgive my sin of omission — and while we're at it, let's not forget about the aurora galleries that show up every so often at SpaceWeather.com. Here's a collection of January's cosmic fireworks.

It's not clear how far the signals will carry, but the broadcast should at least open up a new marketing frontier for Craigslist and its founder, Craig Newmark.

"We wanted to be the first to offer free job postings, apartment listings, personals and other classifieds to the extraterrestrial community," Newmark joked in today's news release. "We believe there could be an infinite market opportunity."

Craigslist's 8 million users will be able to click a checkbox on any of their messages to earmark it for inclusion in a data transmission engineered by Florida-based Deep Space Communications Network. The outfit, which has access to TV production and uplink facilities, put the opportunity up for auction last week.

The recorded high bid was $1,225, but Deep Space's managing director, Jim Lewis, told me that Craigslist might want to transmit more data than his venture was originally offering, requiring a renegotiation of the price.

"We have just about agreed to a price, but we have been asked not to disclose their rate at this time," Lewis said in an e-mail. "Additionally, while Craigslist will be the first, we already have several other transmissions for other clients in the works. We plan on setting some standard pricing soon, so people can easily purchase this service."

Jim Buckmaster, Craiglist's chief executive officer, agreed that the final price would be "significantly higher" than the auction bid. "We'll arrive at something that both sides think is fair," he told me.

Craigslist said the digital postings would be gathered up, along with a video message from Newmark and a clip from the documentary "24 Hours on Craigslist," then transmitted just after the launch of the space shuttle Discovery — which is currently set for May 15.

The hook for the transmission is that aliens far from Earth just might be able to intercept and decode the signals someday. Seth Shostak, an astronomer at the SETI Institute who is heavily engaged in the search for extraterrestrial intelligence, is doubtful about that claim.
His studies
indicate that regular TV transmissions could conceivably be picked up from planets around nearby stars, but even then, they probably could not be deciphered. Also, it's highly unlikely that a relatively brief transmission like the one Deep Space is offering would stand out amid Earth's continuous broadcast babble.

But the folks at Craigslist aren't going to let all that sad-sack science spoil their fun.

"We know that SETI is working on securing a good list of contacts, but we didn't feel right about waiting any longer," Buckmaster said in the news release. "Why not just put the service out there, doesn't have to be perfect at first, and let folks respond with feedback on how we can make it better?"